Biology Reference
In-Depth Information
proportion of S units in the lignin monomers as demonstrated by F5H over-
expressing transgenic poplars. However, other promising results were
obtained thanks to more subtle changes in the lignin polymer, such as the
increase in free phenolic groups obtained in CAD-downregulated trees.
Interestingly, such qualitative modifications generally do not result in much
alteration in tree growth and development.
In addition, until now, most of the studies have been focused on
the evaluation of lignin-modified wood for pulp and paper production.
However, preliminary studies indicated promising results with transgenic
trees modified for C3H, C4H, F5H (
Hinchee, 2011
) and also CCoAOMT
(
van Acker et al., 2011
) for biofuel production. Important efforts are
devoted to the domestication of trees for biofuel production using biotech-
nology, as it may be likely that wood better suited to enhance pretreatment
efficiency may not be available within the genetic variation present in forest
tree natural populations. Due to these important efforts, we may anticipate
that a number of other lignin-modified transgenic trees will be evaluated
for this application in the near future as indicated by a number of applica-
tions in the United States, available at the information systems for biotech-
nology (ISB) website (
http://www.isb.vt.edu/Default.aspxsite
). For
example, a field trial is currently running from 2008 to 2014, in Purdue
University, with different poplar trees modified for virtually all the enzymes
of the lignin biosynthetic pathway (
http://www.isb.vt.edu/getRelDetail.
¼
¼
363-113r
).
3. Effects on the environment
Although a number of studies have concerned the development of lignin-
modified trees in natural conditions and the technological properties of the
modified wood, it is worth stressing that very few studies have been devoted
to the evaluation of potential effects of lignin-modified trees on their envi-
ronment. This probably results from the fact that such studies need specific
field trial design and also requires specific expertise in ecology that is not
necessarily easy to mobilize on the subject. Even if limited in number, these
environmental studies suggest that lignin-modified trees have no or very
limited effects on neighbouring environment. This is probably related to
the fact that the goal for technological applications is to obtain a wood
with somewhat degraded properties for tree physiology, which is unlikely
to increase the fitness of the transgenic trees.
